1. Field of the Invention
The invention relates to a differential having a spring interposed in a compressed state between a surface of a side boss portion of a differential case and a surface of a side gear. The invention also relates to an assembly method of this differential.
2. Description of Related Art
With a differential according to related art described in Japanese Utility Model Application Publication No. 6-80943 (JP 6-80943 U), disc springs are interposed in a compressed state between surfaces of side boss portions of a differential case and corresponding surfaces of side gears, the surfaces opposing each other in an axial direction of the side gears. In this way, the side gears are pressed against pinion gears by the elastic restoring force of the disc springs, thereby reducing backlash between the side gears and the pinion gears.
This kind of a preload-type differential is difficult to assemble. More specifically, although not described in JP 6-80943 U, first, one side gear and the plurality of pinion gears have been set into the differential case. Then, before pinion shafts are assembled to the pinion gears in the differential case, a disc spring is interposed between the surface of one of the side boss portions of the differential case and the surface of one of the side gears, the surfaces opposing each other in the axial direction of the side gear. In the case when the disc spring is interposed, the disc spring must be compressed.
If the disc spring is not compressed, the side gear will end up being pushed upward toward the pinion gear side, with the disc spring in its natural state. As a result, the center of a center hole in this pinion gear will end up being offset with respect to the center of a through-hole for inserting the pinion shaft in the differential case. Therefore, it will be difficult to push the pinion shaft in so that it extends through both the through-hole in the differential case and the center hole in the pinion gear.
In the related art described above, the pinion shaft must be assembled to the pinion gear while the disc spring is compressed by some method, which is difficult to do and may therefore be time consuming.